Secondary direct additives

Both primary and secondary amines add to a /S-unsaturated aldehydes and ketones to yield /3-amino aldehydes and ketones rather than the alternative imines. Under typical reaction conditions, both modes of addition occur rapidly. But because the reactions are reversible, they generally proceed with thermodynamic control rather than kinetic control (Section 14.3), so the more stable conjugate addition product is often obtained to the complete exclusion of the less stable direct addition product. 

Anon, Secondary direct food additives permitted in food for human consumption ethyl acetate. Fed Regist 47(2, BK. 1),145, 1982. (CA96 67362v)... 

Since the order of increasing CL intensity for alkyl amines reacted with Ru(bpy)32+ is tertiary amines > secondary amines > primary amines, pharmaceutical compounds bearing a tertiary amine function (e.g., antihistamine drugs [99], anticholinergic drugs [100], erythromycin [101], and its derivatives [102]) have been sensitively determined after HPLC separation (Table 3). The method was applied to the detection of d- and L-tryptophan (Trp) after separation by a ligand-exchange HPLC [103], The detection limits for d- and L-Trp were both 0.2 pmol per injection. Oxalate in urine and blood plasma samples has also been determined by a reversed-phase ion-pair HPLC (Fig. 18) [104], Direct addition of... 

Secondary direct food additives, 12 30-31 Secondary electrons, in surface imaging, 24 76... 

Although the CuBr/QUINAP system is an effective chiral catalyst in alkynylation of imines or iminiums, one drawback is that enantiopure QUINAP is quite expensive. An analog of QUINAP, PINAP (Figure 5.2), was readily synthesized and found as a very effective chiral ligand in the direct addition of alkynes to iminiums generated from aldehydes and secondary amines in situ (Scheme 5.8). ... 

The direct addition of secondary amides to terminal alkynes has been successfully carried out in the presence of a ruthenium catalyst generated in situ from Ru (methallyl)2(cod) (2 mol%) as metal source, P"Bu3 (6 mol%) and dimethylaminopyr-idine (4mol%), in toluene at 100 °C [54]. Under these conditions the ( )-enamides vere stereoselectively formed from a variety of cyclic amides and ureas (Scheme 10.16). 

Priority-based Assessment of Food Additives (PAFA). It contains administrative, chemical, and toxicological information for over 2000 substances regulated by the FDA as direct, secondary direct, color additives, GRAS substances, and prior-sanctioned substances. In addition, the database contains only administrative and chemical information for less than 1000 such substances. 

Fungal proteases have been investigated extensively in search of suitable milk clotting enzymes. Patents have been issued for production of rennets from E. parasitica, M. Pusillus var. Lindt and M. miehei var. Cooney et Emerson. These have been approved in the United States as secondary direct food additives (FDA. 1984B) and have experienced considerable commercial success in the United States as milk-clotting enzymes for cheese manufacture. Many other fungal sources have also been tried in the effort to find an inexpensive replacement for chymosin. 

Direct addition of H- and other nucleophilic anions to primary, secondary and tertiary alkylsilanes formed pentacoordinate silicate anions (equation 26). Interestingly, the parent silicate, Sills. could not be prepared in this way from silane and hydride65,68. Sills was prepared from alkylhydridosilicates by a hydride transfer reaction (equation 27). The reducing activity of alkylhydridosilicates toward various substrates via hydride transfer in the gas phase was discussed in detail in a previous review67. 

Li and coworkers have reported a novel silver-catalyzed, three-component coupling of an aldehyde, an amine, and an alkyne, and the first example of a direct addition of a silver acetylide to an aldehyde to produce propargylic alcohols (Scheme 1.41).103-105 Treatment of an aldehyde with a silver halide and secondary amine gave propargylic amines in good yields in organic solvent, water, or ionic liquids. The proposed mechanism suggests addition of a silver acetylide to the iminium ion formed in situ. 

A method for synthesis using the reaction of selenoesters with amines or their magnesium salts has been reported. llie reaction of aliphatic selenoesters with various primary alkylamide magnesium bromides in diethyl ether gave -monosubstituted selenoamides, whereas direct addition of secondary amines to selenoesters afforded A -disubstituted selenoamides (Scheme 29). 

The classical method of preparation of amine-trihaloboranes involves the direct addition of the amine to the boron trihalide.1,2 However, when this method is used in an attempt to prepare boron trihalide adducts of secondary amines, one obtains a mixture of... 

The procedure described above illustrates a general, two-step method for the preparation of secondary or tertiary amines. It can be considered as a reductive N-alkylation of a nitrile or an N-monoalkylation of a primary or secondary amine. The first step in the procedure involves direct addition of an aliphatic amine to a nitrile promoted by a stoichiometric amount of cuprous chloride, as fully described recently.4 This method may be used with a large variety of nitriles and primary or secondary aliphatic amines. The nitrile itself may be used as solvent (acetonitrile, benzonitrile). In the case of a primary amine, substrate stoichiometry must be adapted to obtain selectively either the N-monosubstituted amidine [1 eq amine, 1.2 eq Cu(l)CI in acetonitrile] or the N,N-disubstituted amidine [4 eq amine, 1 eq Cu(l)CI, 1 eq acetonitrile in alcohol or DMSO].4... 

Secondary amines like methylaniline can be prepared by the direct addition of an aromatic amine and an alkyl halide —... 

A series of primary and secondary alkyl aryl tellurides has been found to undergo rapid (3-10 min) group-transfer cyclization to afford tetrahydrofuran derivatives in good yields (60-74%) under micro vave heating conditions at 250 °C in ethylene glycol or at 180 °C in vater, the only dra vback of the process being the loss in dia-steroselectivity as a consequence of the higher reaction temperature [22]. Li and coworkers have developed a successful method for synthesis of vinyl cycloethers by direct addition of THF and 1,4-dioxane to alkynes reaction occurs at 200 °C in 40-180 min under the action of microwave irradiation (300 W) [23]. 

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